(BAY-WINGED COW-BIRD.)
[Plate VI. Fig. 1.]
+Molothrus badius+, _Burm. La-Plata Reise_, ii. p. 495 (Paraná and
Tucuman). _Scl. et Salv. Nomencl._ p. 37; _Hudson, P. Z. S._
1874, p. 163 (Buenos Ayres); _Durnford, Ibis_, 1877, p. 174
(Buenos Ayres); _Scl. Cat. B._ xi. p. 338.
_Description._--Dull grey, beneath rather paler; wings chestnut;
tips of primaries, inner portions of secondaries, and tail blackish;
bill and feet black: total length 7·6 inches, wing 3·5, tail 3·0.
_Female_ similar.
_Hab._ Argentina, Paraguay, and Bolivia.
In this species the sexes are alike; the plumage of the body is
grey-drab colour, with a black spot between the eye and beak; tail
dark, the quills cinnamon-colour; beak and legs black. Azara describing
it under the name of _Tordo pardo roxiso_, says it is a rare bird, so
that it has probably greatly increased since his time, as it is now
quite common in the Plata district.
The Bay-wings usually go in small flocks, numbering from ten to thirty
individuals, and are not migratory, but in winter they travel about a
great deal from place to place without extending their journeys more
than a few miles in any direction. They are fond of coming about houses,
and are frequently seen pecking at the fresh meat hanging out of doors;
and, like other birds of the same tribe, feed chiefly on the ground.
They spend a great portion of their time on trees, are familiar with man
and inactive, and in their motions singularly slow and deliberate. Their
language is varied. Curiosity or alarm is expressed by trilling notes,
and before quitting a tree all the birds of a flock ceremoniously invite
each other to fly with long clear notes, powerful enough to be heard a
quarter of a mile away.
They also sing a great deal in all seasons, the song being composed
of soft, clear, rather sweet notes, variously modulated, uttered in a
leisurely manner, and seeming to express a composed frame of mind, all
the birds in a flock singing in concert. During the cold season the
flock always finds some sheltered sunny spot on the north side of a
woodpile or hedge, where they spend several hours every day, sitting
still and singing in their usual quiet, soft style.
Their extreme sociability affects their breeding-habits, for sometimes
the flock does not break up in spring, and several females lay in
one nest together; but whether the birds are paired or practice a
promiscuous intercourse, I have not been able to discover. They have
a great partiality for the large domed nests made by the _Anumbius
acuticaudatus_, called Leñatero in the vernacular. One summer a flock of
about ten Bay-wings took possession of a Leñatero's nest on one of my
trees, and after a few days I took fourteen eggs from it. Though the
birds hopped, chirping round me, manifesting great solicitude, the eggs
were quite cold, and had I left them many more would have been laid, no
doubt; but as they were piled up three or four deep in the nest they
could never have been hatched.
As a rule, however, the flock breaks up into pairs; and then a neat,
well-made nest is built in the fork of a branch, lined with horsehair;
or, oftener still, a Leñatero's nest is seized, the Bay-wings fighting
with great spirit to get possession, and in it, or on it, their own nest
is made. Like their relations, the Common Cow-bird, they seem strongly
attracted by domed nests, and yet shrink from laying in the dark
interior; as a rule when they have captured a Leñatero's nest they break
a hole in the side and so admit the light and form an easy entrance.
One summer a pair of Bay-wings attacked a Leñatero's nest on one of my
trees; the fighting was kept up for three or four days, and then at the
foot of the tree I found five young Leñateros, fully fledged, which had
been pecked to death and thrown out of the nest.
The eggs of the Bay-wing are five in number, nearly round, and densely
marked with dusky reddish brown.
Once I observed two young Bay-wings following a Yellow-breast
(_Pseudoleistes virescens_) with their usual peculiar hunger-cry,
and while I watched them they were fed several times by their
foster-parents. Naturally I concluded that the Bay-winged Cow-bird
is sometimes parasitical on other species, but I never saw anything
afterwards to confirm me in that belief, and I believe now that I was
mistaken, and that the young Bay-wings were not _real_ Bay-wings, but
the young of _Molothrus rufoaxillaris_.